Paper positioning device for feed mechanisms of printing presses and the like



Aug. 15, 1935. w SHACKLETQN 2,011,085

PAPER POSITIONING DEVICE FOR FEED MECHANISMS OF PRINTING PRESSES AND THE LIKE Filed Feb. 21, 1954 3 Sheets-Sheet 1 fiwven/ior 13, 1935. w. H. SHACKLETON 2,011,085

PAPER POSITIONING DEVICE FOR FEED MECHANISMS OF PRINTING PRESSES AND THE LIKE I 5 221W. 4 x H mvew/ior 3y hisAZZorneys 8- 13,1935- w. H. sHAc ETON 2,011,085

PAPER POSITIONING D CE R FEED MECHANISMS OF PRINTING P SES AND THE LI Filed Feb. 21, 1954 3 Sheets-Sheet 5 Invewior fly fiz'sAZZorneys Patented Aug. 13, 1935 a a r 2,011,085:

" UNITED 'STATE-SA- PATENT OFFICE PAPER rosl'rlonmo DEVICE, FOR; FEED MECHANISMS OF PRINTING} PRESSES parts of saidla'st mentioned machine. 1

AND THE LIKE H a William H. Shackleton, 'Wayzat Minn. I Application February 21, 1934, Serial No; 712,338 3 Claims (01: 271--5s)' invention relates to feedingmachinery of the Cross type such as that used in connection,

with printing presses, folding machinesandother paper handling apparatus and particularly relates 1 to an equalizing device for automatically 'so adv justing the position of a sheetof paper about to be delivered from a Cross feeding machine toanother paper handling machine that the sheet will.

be started into said last mentioned machine-in a definite predetermined relation to the moving In Cross feeders considerable inconvenience and waste of paper stock is occasionedby failure of the Cross feeder to stop each sheet of paper in a definite position preparatory-to delivery 'of the sheet to the machinefserved by the Cross feeder. Some thefresult that production is reduced and much.

paper stock is Wasted." I l An object of my invention is to provide an effi-' cient and accurate device for attachment to a Cross fee-ding machine to align the leading edge of. a sheet of paper about tobe deliveredfrom the .Cross feeder toanother paper handling ma may be readily attachedto certain parts'of a Cross feeder, which will obtain its actuating: energy from certain moving parts of the Cross feeder and which will be actuated by said Cross feeder to perform its functions: automatically. It l a Still another object is to provide suchia device including means for pulling asheet "of paper from afposition wherein its edge is adjacent a'predetermined line to a position whereinits edge is at line.

moved fromthe path of a sheet of paper after po- A further object to provide-such a device. wherein all parts thereof 1 are automatically reg j sitioning said sheet so as to permit unobstructed passage of said sheet from the Cross feederto the paper handling machine served by the Cross feeder. N

a A still further object is to provide such a device 5 of inexpensivejsimple and rugged construction andcapable of efiicienua'ccurate'and reliable per-' formance. of its function without damaging or marking papersheets handled thereby.

it These and other objects and advantages of the 10 invention will be more fully set forth in the following description made in connectionwith the accompanying drawings, in which like reference characters refer to similar parts throughout the several views, and in which:-- 5

Fig. 1 isa general top view of certain parts of a Cross feeder with my equalizing device operatively attached thereto;

Fig. 2'is a vertical sectional view taken along the line2 2 ofJFig. 1, s indicated by the arrows, including a. side view of my equalizing device;

Fig. 3 is a side view of my equalizing device and certain parts of a Cross feeder with which it is associated drawn to an enlarged scale and showing the device in one position in full lines and in another position in dotted lines;

l. Fig.4 is 'a vertical sectional view taken along the line 4-4. of Fig. 3 as indicated by the arrows; Fig. 5-is a. side view of my device with certain parts thereof in a partlyoperated position;

Fig. 6 is ahorizontal sectional view taken along the line 6-.-6-of Fig. 3as indicated by the arrows; Fig. :7 is aside view of aportion of another and preferred form of my invention, and

Fig.8 is a sectional view taken along the line 88 of Fig. 7. V

A cross feeder is a machine which, as is well known, in the-printing art, is used to feed sheets of paper stock to other paper handling machines, one sheet atya time. The paper handling machine served by a Cross feeder may be a printing press, afolding machine or some other form of paper handling machine. In any case the cross feeder and. the machine served thereby are so arranged with respect to each other that sheets of paper may run successivelythrough the two machines; as through a single. machine and the two machines are geared together or driven by a common source of power so as to synchronize the motions of the parts of the respective machines. i In the portion of a Cross feeder with which my positioning device is used, sheets of paper are propelled, one at a. time, down a sloping board A lLknown as the lower board, by means of wheels 5 each comber wheel ii there is a comber foot I3 which may be raised and lowered by operating! Mechanism (not shown) is prothe toggle Ito. vided for lowering the foot I? and raising the comber wheel if when a sheet of paper P con trolled thereby has been propelled approximately to a predetermined position. The foot, in contact with the sheet of paper P, arrests motion of the sheet P through frictional engagement therewith. The mechanism for lowering. the comber foot i3 and raising the comber wheel ii is actuated by rockable cut-out shaft i8 011' which is mounted cut-out fingers l8a which are raised by the leading edge of the sheet of paper P as the leading edge approaches said predetermincd position. Cut-out top-guards [9, each having a forked lower end portion, are so'po-sitioned that the cut-out fingers I8a are respec tively located'between the side members of the forked lower end portions of the respective top guards id. The cut-out fingers Isa and the cutout top guards is are located in positions spaced laterally of the Cross feeder from the positions in which my devices are installed. In the approximate predetermined position, referred to above, the leading edge of the sheet of paper P overhangs the forward end of the lower board l9 and is disposed above the feed roll wheels 54 which are continuously rotating. Above the feed roll wheels M, drop roll wheels l5 are supported on swingable arms H50, so that they may be lowered toward the feed roll wheels Hi. The lowering of the'drop roll wheels I?) is effected through mecham'sm (not shown) positively connected to and synchronized with the paper handling machines (such as a printing press or folding machine), to which the Cross feeder delivers sheets of paper. The timing of the drop roll wheel lowering mechanism is so arranged that the drop roll wheels l5 will be lowered each time that the moving-parts of said paper handling machine are in a definite predetermined position. When the drop roll wheels l5 are lowered all the way they press the leading edge portion of the sheet of paper P against the continuously rotating feed roll wheels it which then propel the sheet into said paper handling machine. Since the operating mechanism for dropping the drop roll wheelsv i5 is synchronized with the mechanism of said paper handling machine it is apparent that successive sheets of paper would be fed into said paper handling machine in precisely the same relation to the moving parts of the paper handling machine if, and only if, the leading edge of each sheet is positioned along precisely the same line above the feed roll wheels i i before-the drop roll wheels 55 are lowered. However, in the Cross feeders now in use, such accurate positioning of sheets is notvery closely approximated and the result is that sheets fed to the paper handling machine are not all started into that machine in the samerelation to the moving parts of that machine. This brings about inaccurate results necessitating rejection and wastage of many sheets. One example is roll wheels 65 as will be described.

Referring to the drawings, the parts of my device are mounted on a stationary round spacer bar l6 and a continuously rotating shaft ll, both of which are conventional parts of a cross feeder and extend transversely thereof. For purposes of the following description, the rear end of the Cross feeder will be considered to be the end at which paper stock enters the Cross feeder and, in accordance therewith, the rearmost parts shown arethose in the uppermost portion of Fig. 1 and in the right hand portions of Figs. 2, 3, and 5.

A bracket 20 extends rearwardly and slightly downwardly from the spacer rod l6 and is mounted thereon by means of a portion of the bracket 28 forming a split clamping member 2% which encircles the rod 16 and is drawn into clamping relation therewith by means of screws 20b. The free end portion of the bracket 20,. situated rearwardly and downwardly from theclamping member 2%, is bifurcated to form a spaced pair of lugs 260 and the lugs are respectively horizontally apertured in horizontally aligned portions thereof.

A normally vertically disposed guage plate 2|, having a pair of horizontally aligned and. spaced, horizontally apertured lugs Zia, formed on the medial portion of the rearwardly facing side thereof, is swingably mounted on the lugs 200 of the bracket 20 by means of a pin 22 extending through all of the respective apertures in the lugs 20c and Zia. The gauge plate 2| is provided with a large opening Zle in its medial portion for projection therethrough of the bracketZD. The lower portion of the plate 2| is provided with a notch 22 located centrally between the vertical edges of the plate and extending from the lower edge of the plate to a point a moderate distance thereabove as shown. The notch. 22 divides the lower end portion of the gauge plate 2| into two legs Zlb, at the lower end of each of which is formed a rearwardly projecting and diverging pair of guide lips No, as best shown in Fig. 5.

An adjustable stop screw 23 is mounted in a portion of the bracket 2s so that the head of the screw 23 will serve as a stop engageable with the upper portion of the gauge plate 2! to limit forward movement of said upper portion and hence rearward movement of the lower portion of the gauge plate. A locknut 23a is provided on the screw 23 for use in looking the same in an adjusted position.

The upper end portion of the gauge plate 2| is of reduced width and is provided with a forwardly projecting stud 21d having an aperture therein to which the rear end of a helical tension spring 24 is connected. An apertured lug 25 extends substantially upwardly from the uppermost portion of the clamping member 2% of the bracket 20. A spring anchoring adjustment screw 26 extends through the aperture in the lug 25 and carries an The rear or free end of the able means for normally maintaining the upper portion of the gauge plate'z l in contact 'with the stop screw 23; l

A depending positioning arm 21 is pivotally mounted at'its upper enrich the pin 22 between the lugs 2llcjof thebracket 20 so as to be movable with respect to the bracket 2B and with respect to the gauge plate 21. The lower end portion of the located that, when the finger 28b is in closely spaced relation" with the portion 210 of the arm portion of the gauge plate 21.

arm flextends forwardly in aportion 2111. then downwardly in a portion Z'I'b a-nd rearwardly' in a portion- 210 so as to form a rearwardly opening U-shaped structure comprising the portions 21a,

21b; and 210. The lowermost-portion 21a is cut away at the forwardmost part of its upper side to form 'a shallow notch 21d. and, from this'notch tothe rear end of the portion 210, the upper side of: the portion ilc forms a gripping surface for cooperation with other parts as will be described. A lever 23 extends through an aperture'in the arm 21 located approximately at the'junction of the portions Zlaand 21b of the arm 21 and ispiV- otally mounted therein by means of 'a pin 28a which extends through .the lever 28 and the arm 4 21. Thelower portion of the lever is formed into a flat gripping finger. 28?) having a. lower surface shapedtonest against the gripping surface of the portion-2lc of thearmZl immediately thereabove andin parallel relation thereto when said finger is in'its lowermost'position. The finger 28b and the upper. side "of the portion 21c of the arm 21 comprise a cooperating pair of gripping elements and. the rearmost'portions thereof are shaped to diverge rearwardly with respect to each other. Theparts of my device described above are so 21, the space between the finger 28b and the portion 210 is aligned with the space between the guide lipsZic and also is alignedwith the'upper surface of the lowerboard Hi. The upperarm 28c of the leverl28, extends. upwardly from the pin 28a and at its upper nd is engageable with the forward or free end of a stop 29 which is at-.

tached to and extends forwardly, from the. medial The lower end of a helical tension spring 38. is connected to the upper end portion of the lever-arm 280 by means formed on the rear side of the medial portion of the arm 2'! and a small horizontally apertured lug 21] is formed on the rear side of the arm 21 just above the portion 21a. thereof, 7

A substantially sector-shaped cam 32, having a hub extending from both sides thereofto respectively provide projecting portions 32a and 32b, is

rigidly mounted on the continuously rotating shaft I! previously mentioned. The cam 32 and the projecting portions 320. and32b are split to divide the same into symmetrical halves in order to facilitatemounting of the cam on the shaft Ill. The

projecting portion 320. is provided with clamping ears 32c equipped with clamping screws 32d for 29 mounted onthe gauge plate 2|.

the purpose 01'. holding the two halvesiof the cam 32jtogetherto rigidly grip the shaft IT. The remaining' projecting portion 32biis provided with an annular groove 32c in the peripheral portion thereof. J

A pushrod 33, for oscillating the positioning arm 21, carries at its rea'rward end a forked head or guide yoke 33a, the respective fork members 331) of which are confined in diametrically opposite portions of the annular groove 32elofthe cam hub portion 3212 so as to be forwardly and rearwardly slidable in the groove 32c. A screweye 34 is screw-threadedly mounted in the forward end of thepush-rod33. A lock-nut 34a is mounted on the screw-eye 34 to abut the forward end of thepush-rod 33to retain the screw-eye34in any desired adjustedposition relative to the push rod'33. The forward or eye portion of the screw eye 34 is retained between the halves of the bifurcated lug 21c of the arm 21 by means of a pin 35 extending through the aperturesof the lug 21c and the eye'of the screw-eye 34. 1A downwardly extending apertured lug 330 extends from the lower edge of the forked head 33a adjacent the junction thereof with the pushrod 33. A helical tension spring 36 is connected at its respective ends to the lug 33c and the lug 21] of the positioning arm 21. On the forked head 33a adjacent the point of junction thereof with the push rod 33, a roller 31 is revolubly mounted by means of a pin Slain position to engage the periphery of the cam 32.

In each Cross feeder equipped with my positioning devices at least two of my devices, spaced laterally of the Cross feeden'are installed so that they may act upon a sheet of'paper cooperatively and in unison. i

i Operation As a sheet ofpaperP is propelled down the lower board ID by the comberwheels l L the leading edge of the sheet will strike and operate the cut-out finger l 8a just priorto the sheet reachingfthe. position'thereof .shownin Fig. 3. Operation of the cut-out finger l8a will then cause the comber foot and comber wheel operating mechanism to lower the'comber feetl3 and raise the comber wheels I I to frictionally engage the sheet of paper P toarrestmovement of the sheet when the, leading edge has reached aposition approximating the'position thereofshown in Fig.3. Due to inaccuracy of the mechanism the leading edge of the sheet may stop in apositionsomewhat forward or rearward of that shown. It is to be noted that, in this position, the'leading edge portion of the sheet is disposed'between the'gripping finger 28b and the gripping'surface of the portion 2lc of-the positioning arm .Zlof my device.

Immediately following the above described operation, the continuously rotating cam 32, the

periphery of which is engaged with the roller 31,

forwardly against the tension of the spring 36;

thereby moving the; positioning arm 21 forwardly. As the positioning arm 27 moves for wardlyit oarries the pivot pin 28a, on which the lever 28 is mounted, forwardly with respect tothe stop pin The spring 30 keeps the upper end of the lever 28 in contact with thestop pin 29, resulting in clockwise rotation of the lever 28 relative to the positioning arm 21 as viewed in Fig. 5, until the gripping finger 28b has engaged the sheet of paper P and further relative rotation ofthe lever 28 is prevented by such engagement. Further forward movement of the positioning arm 21 causes the upper end 280 of the lever 28 to leave contact with the stop 29, thus allowing the spring30 to pull the upper end 280 of the lever 28 toward the rear to cause the gripping finger 28b to exert downward pressure and hence tightly grip the sheet of paper P. When the sheet of paper P has been firmly grippedbetween the gripping finger 28b and the portion 210 of the positioning arm 27, it will be drawn forwardly with the arm 21, guided by the guide lips 2 to, until the leading edge of the sheet engages the portions of the gauge plate 2| lying, respectively, between the bases of the guide lips 2 lo of each pair thereof. When such engagement has taken place slippage of the gripping elements 281) and 270 with respect to the sheet of paper P will take place during further forward movement' of the positioning arm 21, thus permitting the sheet of paper to remain stationary with its forward edge in contact with the gauge plate 2|. Just prior to engagement of the forward side of the positioning arm 21 with the rearward side of the gauge plate 2! the point on the gripping ele ments 28b and Z'ic' at which divergence thereof begins has passed the leading edge of the sheet of paper P and all contact between the gripping elements and the sheet has ceased. The sheet will then remain stationary until it is propelled forward by other mechanism as will be described. After engagement between the arm 2? and the gauge plate 2! has taken place, the gauge plate is carried forwardly against the tension of the spring 24 by the arm 27 until the position shown in dotted lines in Fig. 3 has been reached. In this position, it will be noticed, the positioning arm El, the gauge plate 2! and all parts associated therewith are out of line with the sheet of paper P so as to offer no obstruction to further forwardmovement of the sheet. All of the operation so far described has taken place during movement of the cam 32 from a position wherein the roller 3? makes contact with the portion of the cam having minimum radius to a position where the roller has just reached the portion of the cam'having maximum radius. Rotation of the cam may be'oontinued through a considerable angle without effecting any -movement of the parts operated thereby since the portion of the cam having maximum radius'extends through a considerable angle as may be seen in Fig. 3.

The leading edge of the sheet of paper P is now disposed'along a definite line accurately predetermined by the initial or normal position of the gauge plate 2 i and the leading edge portion is disposed above the continuously rotating feed roll wheels M. When the drop roll wheels l are lowered they press the sheet of paper P into frictonal engagement with the feed roll wheels M which then propel the sheet into the machine served by the Cross feeder. Since the mechanism for lowering the drop roll wheels is synchronized with the machine served by the Cross feeder and the leading edge of the sheet is located along a definite predetermined line before lowering of the drop roll wheels occurs, it is apparent that the sheet will bedelivered into the machine served in a definite relation with the moving parts of the machine served. Also, if the operation described above is repeated for delivering other sheets, it is obvious that all of the sheets delivered will pass through the machine served in the same identical relation to the moving parts thereof. Further, if a given sheet is delivered to the machine several times this sheet will pass through the machine in the same relation to the moving parts thereof each time.

After a sheet has been propelled by the feed roll wheels to a point beyond the arm 2'! and the gauge plate 2|, the cam 32 has rotated to a position wherein the roller 31 has passed the end of the portion of the cam having maximum radius. The roller 3'! and the parts to which it is attached are then returned to their initial positions by force exerted by tension in the springs 36 and 24 and force transmitted to the upper end 280 of the lever 28 by the stop 29. The mechanism is then ready for repetition of the cycle of operation described above so as to position another sheet of paper. In practice the described cycle is, of course, continuously repeated for considerable periods of time.

- As has been mentioned, two or more of my positioning devices are used in one Cross feeder and are aligned transversely of the Cross feeder. Accordingly, it is apparent that with devices for pulling two or more points on the leading edge of a sheet to predetermined positions the leading edge is not only pulled up to a given position, longitudinally of the Cross feeder, but is also accurately aligned transversely of the Cross feeder. It will be noticed that various adjustment means are provided in my positioning device whereby the device may be adjusted for smooth and accurate operation. The adjustment screw 23 is adapted for use in setting the gauge plate H to predetermine the position in which the device will place the leading edge of a sheet of paper. The adjustment nut 26a is for adjusting the tension on the spring 24. The adjustment nut 31a is for adjustment of the tension in the spring 3t? and consequently affects the strength with which the gripping elements 28b and 210 will grip a sheet of paper. The screw 34 may be used to alter the relation between the respective normal positions ofthe arm 27 and the gauge plate 2!. Loosening the screws 261) will release the clamp 26a to permit adjustment of the bracket 29 on the spacer rod [6. Loosening of the screws 32d releases the cam 32 so that the same may be rotated on the shaft 9? to properly synchronize the action of my positioning device with the actions of the various moving parts of the Cross feeder.

In the preferred form of my invention partly shown in Figs. '7 and 8, all parts not shown in Figs. '7 and 8 are identical with the corresponding parts of the form of my invention described above and illustrated in Figs. 1 to 6 inclusive and are connected together in the same manner.

A push-rod I33 having a forked head or guide yoke lata with fork members E3373, all of which are identical with the corresponding parts 33a and 33b of the previously described mechanism, is mounted on a screw-eye 34 and locked in position thereon by a locknut I351). The screw-eye is indentieal with the previously described screw-eye 3 3 and is similarly connected to the other parts of the mechanism.

A roller i3! is revolubly mounted on the yoke i330! by means of a pivot pin Mia.

The earn 532 is diametrically split and is mounted on the shaft ii in the same manner as the cam 32 of the previously described form of the invention. A portion i32a extending to one side of the cam 32 carries clamping ears i320 equipped with clamping screws i32d by means of which the cam 532 is fixed to the shaft ii.

A portion i322) projecting from the remaining side of the cam !82, is provided with an annular groove l32e in which portions of the respective guide yoke :1 33a are The groove .i32f which is of a width, onlyslightly greater than the diameter of the roller I31, divides the face of the cam I32 into two ungrooved portions i329 and I32h of which the portion itlg is shaped the same as the'camSZ of the first described form of the invention.

No spring corresponding to the spring 36 of the first described form is used and hence the apertured lugs to which such a spring would be anchored are omitted.

ihe operation of the last described form of my invention is identical'to that of the first form with exceptions to be described. The roller I31 is normally guided at both sides thereof by portions of the cam I32 defining the groove 32! in all positions of the cam I32 exceptthose positions wherein the roller I 31 is bearing against'the circular outer periphery of the cam.

As the cam E32 moves the push-rod 33 forwardly, this movement is not opposed by spring pressure until the positioning arm 21 has made contact with the gauge plate 2|. The remainder of the forward movement is then carried on against the tension of the spring 2 3.

. As rotation of the cam proceeds while thepositioning arm 21 and the gauge plate 2! are in their forwardmost position, the spring 2d exerts a pressure through the gauge plate and the positioning arm to hold the same in contact with each other and to hold the roller I31 in contact with the circular outer periphery of the cam 1132. When the cam I32 has been advanced to a position wherein the roller I3! encounters the open end of the groove I32 the pressure exerted by the spring 23 acts to urge the roller I31 into the groove i321 and to move the gauge plate 2i and the positioning arm 21 rearwardly. This action will continue only until the gauge plate 2| has returned to its normal position wherein its upper portionabuts the stop screw 23, at which time the roller I31 is within the groove I32 of the cam. Continued movement of the cam will result in rearward camming of the roller I31 and rearward movement of the push rod I 33 and the positioning arm 21 entirely free of all spring action until the upper end 280 of the lever 28 makes contact with the stop pin 29. As rotation of the cam is further continued to complete the rearward movement of I the roller I31, the push-rod I33 and the position- Hing arm 21, such movement will be resisted by the spring 38. i

If either the positioning arm 21 or the gauge plate 2i should become obstructed when in their forwardmost positions so as to prevent rearward movement thereof, the roller I31 will not enter the groove I32f as the cam is rotated but instead will engage the circular outer periphery of the cam dislr adjacent the portion I32h of the face of the cam disk. It follows that force will notibe applied to move the obstructed parts rearwardly and hence that the risk of breakage or distortion of the obstructed parts or other parts associated therewith will not be incurred;

Itv is apparentthat I have invented a novel, simple, accurate and inexpensive device for positioning sheets of paper in a Cross feeder,

It is also apparent that my device is readily adaptable for use in many other types of machinery for handling various kinds of sheet material.

Itwill, of courses. be understoodthat various changes maybe made in the form, details, proportions and arrangementof the parts, without departing from the scope of my invention, which,

generally stated, consists in a device capable of carrying out the objects above set forth, in the novelxparts and combinations of parts disclosed and defined in the appended claims.

, Whatis claimed is:-- a

3:1. .Mechanism for accurately positioning sheet material for action thereupon by a machine, having in combination, a sheet support, a gauge plate disposed adjacent said support, a positioning member movable with respect to said plate, gripping means mounted on said member for gripping the leading edge of a sheet of material, apair of guide members mounted on said plate and extending divergently toward said sheet and means for oscillating said member so that the same, when moving in one direction, will pull a sheet gripped by said gripping means into abutment with said gauge plate, said gripping means being constructed and arranged to slip with respect to said leading edge of said sheet when said abutment has taken place whereby said sheet will be positioned with its leading edge aligned with said gauge plate.

2. Mechanism for accurately positioning sheet material for action thereupon by a machine, having in combination, asheet support, a swingable gauge plate located adjacent said support, stop means for limiting movement of said plate in one direction, yieldable means for normally holding said plate in engagement with said step means, a

positioning arm swingably mounted with respect to said plate, means for gripping the leading edge of a sheet disposed on said support, said gripping means being carried by said arm, and means for swinging said arm whereby the same, in the first portion of its movement, will draw the leading edge of said sheet into abutment with said gauge plate, said gripping means being constructed to slip with respect to said sheetwhen further movement takes place after said abutment has been effected and to completely leave contact with said sheet shortly thereafter, said positioning arm being so arranged with respect to said gauge plate that it will abut said plate after said gripping elements have left contact with said sheet and will swing said plate with itself during the last portion of the movement of said arm whereby both said arm and said plate will be disposed entirely out of alignment with said sheet.

' a mechanism for accurately positioning said sheet comprising, a swingable gauge plate mounted slightly forward of the leading edge of an approxiv mately positioned sheet and having a portion alined with said sheet, stop means for limiting rearward movement of said plate, yieldable means for normally holding said plate against said stop means, a positioning arm swingably mounted with respect to said plate, releasable gripping means mounted on said arm for gripping the leading edge of said sheet, means for oscillating said arm, meansactuated through movement of said arm for maintaining said gripping means in nongripping position when said arm is at or near its rearward limit of movement, yieldable means for urging said gripping means into gripping position whereby the overhanging portion of said sheet will be gripped by said gripping means during the first portion of forward movement of said arm and will be drawn into a position wherein the leading edge of said sheet abuts said plate, said gripping means being arranged and constructed to slip with respect to said sheet when said abutment has been efiected and to completely leave 10 contact therewith shortly thereafter, and a lost motion connection between said arm and said plate for transmitting motion from said arm to said plate during the latter portion of the forward movement of said arm following disengagement of said gripping means from said sheet whereby both said arm and said plate will be disposed out of alignment with said sheet when said arm is at or near its forward limit of movement. 

